RTS DV 2400 Series, Руководство по обслуживанию, Страница: 5 / 40

DV-2400
CIRCUIT DESCRIPTION
high and Q104 turns on. Q102 turns on and a voltage is applied to (8T).
The CPU in the control unit monitors the PLL (U205) LD signal directly. When the PLL is unlocked
during transmission, the PLL LD signal goes low. The CPU detects this signal and makes the TXC signal
low. When the TXC signal goes low, no voltage is applied to 8T, and no signal is transmitted. (See Fig. 7.)
SW
Q101
SW
Q102
SW
Q108
SW
Q104
U2 U205
CPU
PLL
LD
RXC
8C
PLL lock
:LD"H"
TXC
8R 8T
.
Fig. 7 Unlock circuit
Transmitter
„
Outline
The transmitter circuit produces and amplifies the desired frequency directly. It FM-modulates the
carrier signal by means of a varicap diode.
„
Power Amplifier Circuit
The transmit output signal from the VCO passes through the transmission/reception selection diode
(D202) and amplified by Q208, Q219, Q212 and Q214. The amplified signal goes to the final amplifier
(Q215) through a low-pass filter. The low-pass filter removes unwanted high-frequency harmonic
components, and the resulting signal is transmitted through the antenna terminal. (See Fig. 8.)
D/A
U505
M62364F
CONVERTER
U504
COM PANDER
AMP
Q5
2SC1623
U500 U504
MIC/IDC
U504
SPLATTER
FILTER
U505
VCO
Q217
2SK1875
NJM2902
MC33111
NJM2902
NJM2902
D/A
M62364F
CONVERTER
BUFFER
Q210
2SC4226
RF AMP
Q207, Q208
2SC4226
X200
192.0MHz
TCXO
PLL
U205
LMX1511TM
RF AMP
Q211
2SC4226
RF AMP
Q219
2SC3356
DRIVE STAGE
Q212
2SK3078A
DRIVE AM P
Q214
AFT05MS
FINAL AMP
Q215
MRF7042
AN T
MIC
BUFFER
006NPB
Fig. 8 Transmitter system
„
APC Circuit
The automatic transmission power control (APC) circuit detects part of a final amplifier output with a
diode (D228, D229) and applies a voltage to U202. U202 compares the APC control voltage (PC)
generated by the D/A converter (U505) with the detection output voltage. U202 generates the voltage to
control Q214 and Q215 and stabilizes transmission output.
The APC circuit is configured to protect over current of Q214 and Q215 due to fluctuations of the load
4